VIDEO: Who are 'Girls' Generation'? South Korean stars win big at YouTube Music Awards

Who are Girls' Generation, the mysterious young women who won big at the YouTube Music Awards?

Justin Bieber, Lady Gaga, Miley Cyrus, One Direction and Selena Gomez: These megastars were some of the contestants for the YouTube Music Awards Video of the Year category. But who took home the honor? That would go to Girls' Generation.

Girls' who? What Generation? Though the pop group won by popular vote at the first annual YouTube Music Awards, which included live performances by Eminem and Lady Gaga, not many people in the U.S. have heard of the South Korean girl group. When co-host Reggie Watts announced the group's win for their flashy, dance-filled music video "I Got A Boy," the audience clapped politely but awkward confusion loomed over the largely American crowd.

So who are Girls' Generation, and how did they win one of the biggest awards from this year's show? Here are five things you need to know:

1. They've been around since 2007: Though the nine young members of the group range in age from 22 to 24, the band has maintained a presence in their native South Korea since 2007. They broke into superstardom with their hit "Gee" in 2009.

2. Two of them are American: Though all of the members share Korean heritage, Tiffany and Jessica were both born and raised in the United States. They were scouted and brought to Seoul, South Korea, to be part of Girls' Generation and finished high schol there.

3. They may release an all-English album in the U.S.: Girls' Generation is in talks with Interscope Records to release a full-length American album based on their Korean album "I Got a Boy," according to TIME.

4. They've sold millions of albums: The band, along with Psy of "Gangnam Style," is the face of the "K-pop" (Korean pop) genre not just in their home country but also in other parts of Asia, especially Japan, where the group released special versions of their albums.

5. They're so famous, someone recognized their limbs: One member of the band told the New Yorker about the time a few of them tried to go out and disguise themselves. But their fans recognized them just by the shape of their limbs. "It's just so freakishly cool!" said Tiffany.